A new generalization of alpha-skew-normal distribution

In this paper, a new generalization of alpha-skew-normal distribution is considered. Some properties of this distribution, which is denoted by GASN(α, λ), including moments, maximum likelihood estimation of parameters, and some other properties are studied. Finally, using a real data set, we show that our new distribution is the best-fitted distribution for the used data among normal, skew normal, alpha-skew-normal, and skew-bimodal-normal distributions.     

The Assessment of Quality of Life in Transitional Neighborhoods

Quality of life (QoL) is being considered as one of the fundamental concepts in contemporary era. It tries to assess the level of general welfare of the communities. Urban transitional neighborhoods possess specific situation and as a result present distinctive QoL. The major objective of this study is to identify and measure the QoL dimensions in urban transitional neighborhoods using both objective and subjective indices pertaining to Darvazeshemiran neighborhood of Tehran. In order to accomplish this and gather needed data, 244 questionnaires were distributed among Darvazeshemiran’s residents. This study suggests that there exists low level of QoL in the study area. That is 64.3 % of the residents were dissatisfied with the prevailing level of QoL. This in turn is associated with the transitional nature of this neighborhood. The residents were strongly dissatisfied with regard to the environmental qualification as opposed to accessibility status. Furthermore, this study identified five objective factors respectively regarding QoL. There exists low correlation between subjective and objective dimensions. That demands simultaneous consideration of both objective and subjective dimensions. It is argued that individual treatments of each could not accurately represent the QoL of residents.     

An Additive–Multiplicative Restricted Mean Residual Life Model

The mean residual life measures the expected remaining life of a subject who has survived up to a particular time. When survival time distribution is highly skewed or heavy tailed, the restricted mean residual life must be considered. In this paper, we propose an additive–multiplicative restricted mean residual life model to study the association between the restricted mean residual life function and potential regression covariates in the presence of right censoring. This model extends the proportional mean residual life model using an additive model as its covariate dependent baseline. For the suggested model, some covariate effects are allowed to be time‐varying. To estimate the model parameters, martingale estimating equations are developed, and the large sample properties of the resulting estimators are established. In addition, to assess the adequacy of the model, we investigate a goodness of fit test that is asymptotically justified. The proposed methodology is evaluated via simulation studies and further applied to a kidney cancer data set collected from a clinical trial.     

Time series models based on the unrestricted skew-normal process

The standard location and scale unrestricted (or unified) skew-normal (SUN) family studied by Arellano-Valle and Genton [On fundamental skew distributions. J Multivar Anal. 2005;96:93–116] and Arellano-Valle and Azzalini [On the unification of families of skew-normal distributions. Scand J Stat. 2006;33:561–574], allows the modelling of data which is symmetrically or asymmetrically distributed. The family has a number of advantages suitable for the analysis of stochastic processes such as Auto-Regressive Moving-Average (ARMA) models, including being closed under linear combinations, being able to satisfy the consistency condition of Kolmogorov’s theorem and providing the guarantee of the existence of such a SUN stochastic process. The family is able to be represented in a hierarchical form which can be used for the ease of simulation. In addition, it facilitates an EM-type algorithm to estimate the model parameters. The performances and suitability of the proposed model are demonstrated on simulations and using two real data sets in applications.     

Effect of immediate and continuous mother–infant skin-to-skin contact on breastfeeding self-efficacy of primiparous women: A randomised control trial

ObjectiveTo evaluate the effect of mother–infant immediate skin-to-skin contact on primiparous mother's breastfeeding self-efficacy.Study designA randomised control trial.SettingsThe study was conducted in Omolbanin obstetrics hospital (large tertiary hospital), Mashhad, Iran.Participants114 18–35 year-old primiparous, Iranian, healthy and full term mothers who anticipated normal vaginal delivery and intended to breastfeed their babies.InterventionSkin-to-skin contact immediately after birth and then controlling breastfeeding self-efficacy at 28 days postpartum.Main outcome measureMaternal breastfeeding self-efficacy at 28 days postpartum and success in first breastfeeding and mean time of first breastfeeding initiation.ResultsA total of 92 mother–infant dyads (47 dyads in skin-to-skin care skin-to-skin contact group and 45 dyads in routine care group) were monitored and analysed. In skin-to-skin contact group, breastfeeding self-efficacy was 53.42 ± 8.57 SD as compared to 49.85 ± 5.50 SD in routine care group which is significantly higher in skin-to-skin contact group (p = 0.0003).Successful breastfeeding initiation rate was 56.6% in skin-to-skin contact group as compared to 35.6% in routine care group (p = 0.02).Time to initiate first feed was 21.98 ± 9.10 SD min in SSC group vs. 66.55 ± 20.76 min in routine care group (p < 0.001).ConclusionMother–infant immediate skin-to-skin contact is an easy and available method of enhancing maternal breastfeeding self-efficacy. High breastfeeding self-efficacy increases exclusive breastfeeding duration.     

Im/mobile highly skilled migrants in Qatar*

Most studies on the mobility of highly skilled migrants have been examined with a framework of global talent mobility and under conditions of neoliberal governance and economic globalization. In this study we challenge the notion of the hypermobile knowledge worker. Utilizing mixed methods, we examine the factors that attracted highly skilled migrants to Qatar and the conditions under which they might leave in the future. Rather than finding a group of footloose migrants attracted primarily to high-wage jobs, a lack of taxation or amenities, and with multiple alternative locations of residence, we find that highly skilled migrants exist on a spectrum of immobility. More significantly, this immobility depends on the migrant’s region of origin. For Asian and Western migrants immobility is attributed to the Kafala system or employer sponsorship, which hinders occupational and spatial mobility and ties workers to their sponsors. Arab highly skilled migrants are especially affected by lack of security and stability in their home countries, which makes these workers involuntarily immobile. The former group seem to be willing to accept a reduced level of agency and mobility for high income, whereas for the latter security and stability are more fundamental to their decision to come to Qatar.     

Monitoring and change-point estimation for spline-modeled non-linear profiles in phase II

In some applications of statistical quality control, quality of a process or a product is best characterized by a functional relationship between a response variable and one or more explanatory variables. This relationship is referred to as a profile. In certain cases, the quality of a process or a product is better described by a non-linear profile which does not follow a specific parametric model. In these circumstances, nonparametric approaches with greater flexibility in modeling the complicated profiles are adopted. In this research, the spline smoothing method is used to model a complicated non-linear profile and the Hotelling T² control chart based on the spline coefficients is used to monitor the process. After receiving an out-of-control signal, a maximum likelihood estimator is employed for change point estimation. The simulation studies, which include both global and local shifts, provide appropriate evaluation of the performance of the proposed estimation and monitoring procedure. The results indicate that the proposed method detects large global shifts while it is very sensitive in detecting local shifts.     

Exponentiated power Lindley power series class of distributions: Theory and applications

ABSTRACT

We introduce a new four-parameter generalization of the exponentiated power Lindley (EPL) distribution, called the exponentiated power Lindley power series (EPLPS) distribution. The new distribution arises on a latent complementary risks scenario, in which the lifetime associated with a particular risk is not observable; rather, we observe only the minimum lifetime value among all risks. The distribution exhibits a variety of bathtub-shaped hazard rate functions. It contains as particular cases several lifetime distributions. Various properties of the distribution are investigated including closed-form expressions for the density function, cumulative distribution function, survival function, hazard rate function, the rth raw moment, and also the moments of order statistics. Expressions for the Rényi and Shannon entropies are also given. Moreover, we discuss maximum likelihood estimation and provide formulas for the elements of the Fisher information matrix. Finally, two data applications are given showing flexibility and potentiality of the EPLPS distribution.     

A Discourse on the Incorporation of Organizational Factors into Probabilistic Risk Assessment: Key Questions and Categorical Review

This article presents a discourse on the incorporation of organizational factors into probabilistic risk assessment (PRA)/probabilistic safety assessment (PSA), a topic of debate since the 1980s that has spurred discussions among industry, regulatory agencies, and the research community. The main contributions of this article include (1) identifying the four key open questions associated with this topic; (2) framing ongoing debates by considering differing perspectives around each question; (3) offering a categorical review of existing studies on this topic to justify the selection of each question and to analyze the challenges related to each perspective; and (4) highlighting the directions of research required to reach a final resolution for each question. The four key questions are: (I) How significant is the contribution of organizational factors to accidents and incidents? (II) How critical, with respect to improving risk assessment, is the explicit incorporation of organizational factors into PRA? (III) What theoretical bases are needed for explicit incorporation of organizational factors into PRA? (IV) What methodological bases are needed for the explicit incorporation of organizational factors into PRA? Questions I and II mainly analyze PRA literature from the nuclear domain. For Questions III and IV, a broader review and categorization is conducted of those existing cross-disciplinary studies that have evaluated the effects of organizational factors on safety (not solely PRA-based) to shed more light on future research needs.